Method of rolling tubes with internally thickened ends



Feb. 21, 1933. KLEIN 1,898,779

METHOD OF ROLLING TUBES WITH INTERNALLY THICKENED ENDS Filed Sept- 22, 1930 i 1 4 4 $my 67 fiver/for: L. K/ein L I /M w Patented Feb. 21, 1933 UNITED STATES PATENT OFFICE LUDWIG KLEIN, OF DUSSELDORF, GERMANY, ASSIGNOR TO THE FIRM VEBE INIGTE STAHLWERKE AKTIENGESELLSCHAFT, 0F DUSSELDORF, GERMANY METHOD OF ROLLING TUBES WITH INTERNALLY THICKENED ENDS Application filed September 22, 1930, Serial No. 483,630, and in Germany February 8, 1930.

Tubes with thickened ends, such as are used mainly as bore rod tubes, have liltherto been made in various ways.

Thus according to one method the walls at the ends are thickened by the ends being upset and according to another method the thickening produced by rolling the tube ends with an external thickening is brought to the inside by repeated forging.

These methods have the great disadvantage that the material suffers through having to be several times heated, so that the durability of the tubes is seriously affected.

It has also been proposed to roll out a normal sleeve-shaped blank in a pilgermg mill either over a mandrel having an offset portion or over a normal mandrel not inserted right up to the forward end of the sleeve. As in these pilgering methods the rear end of the sleeve rests against a shoulder on the mandrel or against a stripper, when rolling out the thickened part and the portion of the tube adjoining it a difierent part of the tube will at each pilgering. stage of the rolling mill come against the mandrel shoulder or against the forward end of the mandrel, as, owing to the sleeve being supported at its rearward end, the material can expand only forwards. Consequently in this method it is impossible to prevent overlappings being formed at the place of transition from the thickened part to the normal part of the tube, which consist in depressions and shoulders both on the external and on the internal surface of the tube and seriously affect the usefulness of a tube rolled out in this way or may even make it useless.

The method according to the invention has for its object to provide the tube to be rolled with an annular constriction before the actual pilgering operation at the place where in the finished product the thickened tube end merges into the normal thickness of the tube wall.

An essential feature of thenew method consists in this, that the tube provided with the constriction is rolled out over a mandrel, a shoulder of which rests against the said constriction, such that the material can expand rearwards for at least as long as the rolls are acting at the place where the mandrel shoulder is situated.

During the rolling out of the thickened tube end over the offset part of the mandrel and during the period in which the rolls in rolling out the material over the part of the mandrel of normal thickness are still acting at the offset part of the mandrel to the constriction, the tube rests with the annular constriction against the shoulder of the mandrel, while the rear end of the blank does not abut against anything, so that a rearward expansion of the material is actually ensured. Only from the moment at which the rolls cease to act at the place where the mandrel is offset, the rear end of the tube will rest in a known manner against a stop on the mandrel or against the stripping sleeve so that from that moment onwards the material will expand in the normal way, that is, forwards.

Tubes made in accordance with the new method with internally thickened ends have the considerable advantage, owing to the constriction in the tubes and owing to the possibility of free expansion rearwards during the rolling out of the thickened part and the normal parts of the tube directly adjoining the thickened part, that they will show no overlappings and that they constitute products of unexceptional quality which are immediately ready for use.

In the accompanying drawing Figs. 1, 2, 3 and 4 are longitudinal sectional viewsthrough a rolling mill showing four stages in accordance with the improved rolling method. The normally holed blank a is constricted before the commencement of the rolling operation proper, preferably in connection with the holing process, at a distance from the end corresponding to the desired length of the thickened part, to such an extent that the thin part b, of the mandrel will just pass through the constricted place. The blank a is thereby provided at the place of transition to the thick part b of the mandrel with an abutment with which it rests at the beginning of the pilgering operation (Figure 1) against the shoulder 6 on the mandrel, a free 5 ace d being left between the rear end of t e blank a and the stripping sleeve 0 and the length of the space being such that the blank a can expand rearwards.

During the pilgering operation, the end of the blank a lying in front of the constriction is rolled down'on the thin art b of the mandrel to form the thickened tube end. As soon as the rolls operate over the dangerous offset 6 of the mandrel (Fig. 2) the blank will be forced during each operation of the rolls toward the free space (2 and can freely expand. If the end of the blank a is on the stripping sleeve 0 the rolls have already passed beyond the danger zone 6 (Fig. 3). From this moment, the rolling down of the tube a will take place in the normal way, that is to say, the material will expand forwards as shown in Figure 4.

What I claim is:

1. A method of pilgering tubes with internall thickened ends, consisting in forming in t e tubular blank near the end an annular constriction at a distance corresponding to the desired length of the thickened 0rtion and thereupon subjecting the blan to the pilgering operation proper, as and for the purpose set forth.

2. A method of pilgering tubes with internally thickened ends, consisting in forming in the tubular blank near the end an annular constriction at a distance corres 0nding to the desired length of the thic ened portion and thereupon rolling down the blank over a mandrel having a shoulder which rests against the said constriction, such that up to the'time when the rolls cease to engage at the place where the shoulder on the mandrel is located the material of the blank can ex and rearwards, as and for the purpose set orth.

In testimony whereof I afiix my signature.

LUDWIG KLEIN. 

